Falling fluid heat exchanger and evaporator



1966 TAIICHI TAKAHASHI 3,279,525

FALLING FLUID HEAT EXCHANGER AND EVABORATOR Filed March 12, 1965 QQQQQKQKQQ FIG. I I0 Patented Oct. 18, 1966 3,279,525 FALLING FLUID HEAT EXCHANGER AN D EVAPORATOR Taiichi Takahashi, 76 S-chome, Tamagawa-todoroki-cho,

Setagaya-ku, Tokyo, Japan Filed Mar. 12, 1965, Ser. No. 439,245 Claims priority, application Japan, May 6, 1964,

9/ 25,311 7 Claims. (Cl. 159-3) This invention relates to falling fluid heat exchangers and falling fluid evaporators utilizing the same.

An object of the present invention is to provide a heat exchanger wherein the heat transfer resistance between the heat transfer pipe and the fluid outside the pipe is reduced and wherein the heat transfer area is substantially increased and consequently the over-all heat transfer coeflicient is improved.

Another object of the present invention is to provide a falling fluid evaporator wherein, by utilizing said heat exchanger, the total heat transfer area of the evaporator is increased, wherein the over-all heat transfer coeflicient between the fluid to be evaporated and the heating steam is increased, and wherein the amount of evaporation per evaporator is increased and at the same time the fluid to be concentrated can be taken out within a reduced heating time.

The fluid so called in the specification and claims shall mean a solution, a mixture of liquids or apmixture of a liquid and a solid.

The conventional evaporators are mostly of a submerged pipe type wherein the inside or outside of the heating pipe is submerged in a fluid. However, there has recently appeared an evaporator wherein a liquid film flows down within a single vertical pipe of a comparatively large caliber and is heated from the jacket part outside the pipe. It is difficult therein to increase the heat transfer area so as to increase the evaporating capacity per unit. Y

The present invention relatesv more particularly to a heat exchanger comprising a bank of tubular heating pipes arranged substantially hon'zontallyin the space within an evaporator casing and cylindrical heat transferring structure mounted for rotation on the pipes and annularly spaced therefrom, said structures having fins extending therefrom and extending substantially parallel to the axes of the heat transferring structures and provided with perforations allowing the free passage of fluid so that the fluid to be concentrated may be made to fall from above the bank of the pipes and may rotate said cylinder heat transferring structure whereby heat may be exchanged, and to a falling fluid evaporator utilizing such heat exchanger.

The other objects and effects of the present invention will become clear from the following description with reference to the accompanying drawings in which:

FIGURE 1 is a cross-sectional illustrative view of the essential part of an evaporator embodying the present invention;

FIGURE 2 is a perspective view of a part of the cylindrical heat transferring structure shown in FIGURE 1;

FIGURE 3 is an end view of a modification of the cylindrical heat transferring structure;

FIGURE 4 is a perspective view of a part of another modification of the cylindrical heat transferring structure; and

FIGURE 5 is a perspective view of another modification of the cylindrical heat transferring structure.

In FIGURES l and 2, 1 is an evaporator casing, 2 is a bank of tubular heating pipes arranged substantially horizontally within the evaporator casing 1, and 3 is a cylindrical heat transferring structure rotatably mounted on each heating pipe 2 and provided with perforations allowing the free passage of fluid therethrough and with pins 5 extending substantially parallel to the axes of the structures 3. The fins of the cylindrical heat transferring structure shown in FIGURE 2 are made by punching. 6 is a sprinkler for fluid to be concentrated and it is arranged above the bank of the heating pipes 2. 7 is a packing to prevent sprays of the fluid from escaping together withthe evaporated steam. 8 is an outlet for the evaporated steam. The evaporated steam is led through said outlet to a normally used condenser (not illustrated) which is generally connected to a vacuum sys- .tem. 9 is a pipe to lead the fluid from a reservoir (not illustrated) to the sprinkler 6. 10 is an outlet pipe for the concentrated liquid. 11 is a pipe to connect the pipes 9 and 10. A pump 12 is provided in the pipe 11.

The operation of the heat exchanger of the present invention shall now zbe explained.

The fluid falling from the sprinker 6 will pass through the perforations 4 allowing its free passage and will fill the space between the heating pipe 2 and the heat transferring structure 3. On the other hand, the cylindrical heat transferring structure having the fins thereon will be rotated like a water-mill by the falling fluid.

In such case, the fluid filling the space between the heating pipe 2 and the heat transferring structure 3 will have the effect of a lubricant and will help therotation of the cylindrical heat transferring structure around the heating pipe. On the other hand, because the cylindrical heat transferring structure is rotatable like a water-mill, vthe fluid staying on the surface of the pipe will be well stirred, the thickness of the so-called laminar liquid film 'of less fluidity on the surface of the heating pipe will be reduced and the heat transfer coeflicient between the heating .pipe and the fluid will be increased. When the apparatus is utilized in an evaporator, the fluid will be evaporated through the perforations allowing its free passage and the amount of evaporation will be increased. Further, as sufficient stirring is made, there is an effect that, in the case of heating such fluid which tends to produce crystals or scales or which is so comparatively high in viscosity as not to he fluid and has a tendency to increase the thickness of the laminar liquid film, the'overallheat transfer coeflicient will be increased. There is also an eflect that, when a fluid which tends to bubble is to be evaporated, the free surface area of the fluid will become so large that the leakage out of the evaporator may be reduced.

By varying the construction and dimensions of the fins on the rotatable structure and the amount of the falling fluid, the rotating speed can be varied. Further, it can be made interchangeable with another cylindrical heat transferring structure of other construction and dimensions and which is rotatable like a water-mill.

As the inside surface of the structure is in contact with the heating pipe or the laminar liquid film in some part, there is an operational effect of increasing the heat transfer area.

In an evaporator in which the heat transfer resistance is higher in the heated fluid side of the pipe than in the steam side of the pipe, it acts directly to increase the evaporating capacity.

The cylindrical heat transferring structure illustrated in FIGURE 3 has at least three rollers 13 on the inside surface thereof so that its rotation takes place easily. In this case, the stirring of the fluid over the pipe is made by running of these rollers. Rollers may be set on the side surface of each end of the cylindrical heat transferring structure. In this case, the clearance between the inner surface of the structure and the outer surface of the pipe is preferably so small that the stirring of the fluid over the pipe may be made. The cylindrical heat transferring structure illustrated in FIGURE 4 has per- 1 forations consisting of many small holes 4' between each' perforation 4 is formed between the adjacent fins 5. Further, the bearing '14 consists of two semicircular members connected with each other with screws or stud bolts 15. By such construction,'the rotation can be made smooth, the fluid can be prevented from flowing out through both ends and the parts can be removed and fitted as required. The bearings may be either roller hearings or ball bearmgs.

It is preferable that the rotatablecylindrical heat transferring structure be made of a metal of a heat transfer coefiicient as high as possible and a small weight and easy to work. The construction, material and dimensions of the cylindrical heat transferring structure are selected by taking the corrosion by the fluid and the rotating speed into consideration. As material, there canbe used not only iron and steel but also stainless steels, light metals, copper alloys, titanium and lead alloys. However, if required, impervious graphite or any other anti-corrosion material can be also used. I 7

When the apparatus is to be utilized as an evaporator, if the falling fluid is passed once, it will be able to be taken out within a reduced heating time. Therefore, the unit can be used also to heat and/or concentrate within a short time liquids containing vitamin, fruit juice, milk or any other organic substance and likely to be decomposed by heat. There can be plural passages of the fluid by repeatedly making the fluid 'fall by using the pump 12. Further, it is easy to use the present apparatus as a vacuum evaporator. However, it can 'be used also as a multi-eflect evaporator. described above, a bank consisting of many pipes can be formed within a single unit and the total vof the heat transfer areas can be made large. Therefore, an evaporator of a large capacity can be formed in a given space. Further, as no power is used for stirring, there is no need for a precision finish, any consideration of such problem of leakage from outside as in rotary shafts, any excess material and cost in the operation and maintenance and any diflicult specific care to be taken in the operation.

The evaporator of the present invention has the effect of reducing the heat transfer resistance outside the pipe, that is, on the fluid side, and increasing the heat transfer area on the fluid side and elevates the over-all heat transfer coefiicient. Therefore, it can be used not only as an evaporator but also as a general heat exchanger. Such heat exchanger also falls under the scope of the present invention. Illustrated are a few embodiments of the present invention. The present invention is not limited to them but is limited as set forth in the following claims.

What is claimed is:

- sprinkler, said fluid may be evaporated by a heating me:

In the present apparatus, as

1. A falling fluid evaporator comprising a casing, a bank of tubular heating pipes arranged substantially horizontally in the space within said evaporator casing, cylindrical heat transferring structures mounted for rotation on the pipes and annularly spaced therefrom, said structures having fins extending therefrom and extending substantiak ly parallel to the axes of the heat transferring structures and provided with perforations allowing the free passage of a fluid, and a sprinkler set above said bank oflthe pipes so that, while said cylindrical heat transferring structures are being rotated by the fluid falling from said dium in said bank of the heating pipes.

2. A heat exchanger comprising a substantially horiizontaly arranged bank of tubular pipes, cylindrical heat fins extending therefrom and extending substantially par-' allel to the axes of the heat transferring structures and provided with perforations allowing the free passage of, a fluid and a sprinkler set above said bank of the pipes so that, while said cylindrical heat transferring structures are being rotated by the fluid falling from said sprinkler, a heat exchange may take place between said fluid and a heat transfer medium in said bank of the pipes.

3.'The evaporator according to claim 41 wherein said perforations are narrow long openings corresponding to the respective fins.

4.-The evaporator according to claim :1 wherein said cylindrical heat transferring structures are provided with at least three rollers at their ends in contact withtheir respective heating pipes.

5. The evaporator according to claim 1 wherein the perforations in said cylindrical heat transferring structures consist of a plurality of small holes.

6. The'evaporator according to claim 1 wherein said cylindrical heat transferring structures are made separable into at least two parts.

7. The evaporator according to claim 1 wherein-said cylindrical heat transferring structures are provided with bearings at both' ends.

References Cited by the Examiner UNITED STATES PATENTS 415,541 11/1889 Lee 159-7 1,200,996 10/1916 Soderlund et a1 159 24 "1,536,894 5/1925 Lillie 159-13 1902533 3/1933 Vykoupil [159-17 2,876,833 3/1959 Kelley et al. 159-4 FOREIGN PATENTS 176,175 10/1906 Germany.

NOR-MAN YUDKOFF, Primary Examiner. J. 'SOFER, Assistant Examiner. 

1. A FALLING FLUID EVAPORATOR COMPRISING A CASING, A BANK OF TUBULAR HEATING PIPES ARRANGED SUBSTANTIALLY HORIZONTALLY IN THE SPACE WITHIN SAID EVAPORATOR CASING, CYLINDRICAL HEAT TRANSFERRING STRUCTURES MOUNTED FOR ROTATION ON THE PIPES AND ANNULARLY SPACED THEREFROM, SAID STRUCTURES HAVING FINS EXTENDING THEREFRON AND EXTENDING SUBSTANTIALLY PARALLEL TO THE AXES OF THE HEAT TRANSFERRING STRUCTURES AND PROVIDED WITH PERFORATIONS ALLOWING THE FREE PASSAGE OF A FLUID, AND A SPRINKLER SET ABOVE SAID BANK OF THE PIPES SO THAT, WHILE SAID CYLINDRICAL HEAT TRANSFERRING STRUCTURES ARE BEING ROTATED BY THE FLUID FALLING FROM SAID SPRINKLER, SAID FLUID MAY BE EVAPORATED BY A HEATING MEDIUM IN SAID BANK OF THE HEATING PIPES. 